Traffic management for materials handling vehicles in a warehouse environment

ABSTRACT

Systems and methods for a materials handling vehicle to navigate a vehicle transit surface in a warehouse environment including a navigation subsystem configured to cooperate with a traction control unit, a braking system, a steering assembly, and an obstacle detection subsystem to: determine whether the materials handling vehicle is approaching, or has arrived at, a potentially contested intersection; associate with the intersection pre-positioned warehouse object data, a set of road rules, and obstacle data; and navigate the materials handling vehicle through the intersection utilizing warehouse navigation maneuvers in combination with the associated set of road rules, obstacle avoidance maneuvers, or both, the warehouse navigation maneuvers accounting for the associated pre-positioned warehouse object data and the obstacle avoidance maneuvers accounting for the obstacle data derived from the obstacle detection subsystem.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Non-Provisional applicationSer. No. 16/861,935 (CRNZ 1627 NA), filed Apr. 29, 2020, which is acontinuation of U.S. Non-Provisional application Ser. No. 16/046,400(CRNZ 1627 PA), filed Jul. 26, 2018, which claims the benefit of U.S.Provisional Application Ser. No. 62/537,981 (CRNZ 1627 MA) filed Jul.28, 2017, the entireties of which are incorporated by reference herein.

BACKGROUND

The present disclosure generally relates to systems and methods fortraffic management, and, more specifically, to systems and methods fortraffic management in a warehouse environment between manual,semi-autonomous, and/or autonomous materials handling vehicles.

BRIEF SUMMARY

In accordance with one embodiment of the present disclosure, a materialshandling vehicle is provided, and comprises an obstacle detectionsubsystem and a navigation subsystem. The navigation subsystem isconfigured to cooperate with the traction control unit, the brakingsystem, the steering assembly, and the obstacle detection subsystem ofthe vehicle to: determine whether the materials handling vehicle isapproaching, or has arrived at, a potentially contested intersection;associate pre-positioned warehouse object data derived from a databaseof pre-positioned warehouse objects in the warehouse environment withthe potentially contested intersection; associate a set of road ruleswith the potentially contested intersection; and associate obstacle dataderived from the obstacle detection subsystem with the potentiallycontested intersection. The navigation subsystem is further configuredto cooperate with the traction control unit, the braking system, thesteering assembly, and the obstacle detection subsystem to navigate thematerials handling vehicle through the potentially contestedintersection utilizing warehouse navigation maneuvers in combinationwith the associated set of road rules, obstacle avoidance maneuvers, orboth. The warehouse navigation maneuvers account for the associatedpre-positioned warehouse object data and the obstacle avoidancemaneuvers account for the obstacle data derived from the obstacledetection subsystem.

In accordance with another embodiment of the present disclosure, asystem comprising a remote terminal and a materials handling vehicle isprovided. The materials handling vehicle comprises an obstacle detectionsubsystem and a navigation subsystem that is configured to communicatewith the remote terminal. The remote terminal is configured to maintainthe database of pre-positioned warehouse objects.

In accordance with yet another embodiment of the present disclosure, amethod of navigating a materials handling vehicle with respect to avehicle transit surface in a warehouse environment is provided.According to the method, the navigation subsystem of the materialshandling vehicle is used to determine whether the materials handlingvehicle is approaching, or has arrived at, a potentially contestedintersection. Pre-positioned warehouse object data, a set of road rules,and obstacle data are associated with the potentially contestedintersection. The method further comprises navigating the materialshandling vehicle through the potentially contested intersectionutilizing warehouse navigation maneuvers in combination with theassociated set of road rules, obstacle avoidance maneuvers, or both.

In accordance with yet one other embodiment of the present disclosure, atraffic management system is provided comprising a remote or localtraffic management server configured to grant permission to submittedvehicle requests to proceed through an intersection based on clearanceof prior submitted requests and corresponding exit notifications.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and are not intended to limit the subject matter defined bythe claims. The following detailed description of specific embodimentsof the present disclosure can be best understood when read inconjunction with the following drawings, where like structure isindicated with like reference numerals and in which:

FIG. 1A schematically illustrates an implementation process for aremotely mediated embodiment, according to one or more embodiments shownand described herein;

FIG. 1B schematically illustrates an implementation process for alocally mediated embodiment, according to one or more embodiments shownand described herein;

FIG. 2 schematically illustrates an example of the implementationprocess of FIGS. 1A or 1B as applied to a mediated materials handlingvehicle approaching an intersection, according to one or moreembodiments shown and described herein;

FIG. 3A schematically illustrates an implementation process for amaterials handling vehicle-sensor mediated embodiment, according to oneor more embodiments shown and described herein;

FIG. 3B schematically illustrates another implementation process for amaterials handling vehicle-sensor mediated embodiment, according to oneor more embodiments shown and described herein;

FIG. 3C schematically illustrates an example of the implementationprocess of FIGS. 3A or 3B as applied to a mediated materials handlingvehicle approaching an two-way aisle intersection to cross straightthrough the intersection and a respective give way region, according toone or more embodiments shown and described herein;

FIG. 3D schematically illustrates an example of the implementationprocess of FIGS. 3A or 3B as applied to a mediated materials handlingvehicle approaching the two-way aisle intersection to turn right intothe intersection and a respective give way region, according to one ormore embodiments shown and described herein;

FIG. 3E schematically illustrates an example of the implementationprocess of FIGS. 3A or 3B as applied to a mediated materials handlingvehicle approaching a one-way aisle intersection to cross straightthrough the intersection and a respective give way region, according toone or more embodiments shown and described herein;

FIG. 3F schematically illustrates an example of the implementationprocess of FIGS. 3A or 3B as applied to a mediated materials handlingvehicle approaching the one-way aisle intersection to turn right intothe intersection and a respective give way region, according to one ormore embodiments shown and described herein;

FIG. 4A schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle approaches a clearintersection and has the right of way;

FIG. 4B schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have the right ofway when approaching an intersection with another materials handlingvehicle positioned in a left approach zone of the intersection;

FIG. 4C schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have the right ofway when approaching an intersection at which an obstacle blocks amaterials handling vehicle-sensor field of view of a left approach zoneof the intersection;

FIG. 4D schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle has the right of way whenapproaching an intersection with another materials handling vehiclepositioned in a right approach zone of the intersection;

FIG. 4E schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle has the right of way whenapproaching an intersection with an obstacle blocking a materialshandling vehicle-sensor field of view of a right approach zone of theintersection;

FIG. 4F schematically illustrates a scenario where a mediated materialshandling vehicle has the right of way when crossing straight through anintersection with another oppositely facing materials handling vehiclepositioned across the intersection to cross straight through theintersection;

FIG. 4G schematically illustrates a scenario where a mediated materialshandling vehicle has the right of way when crossing straight through anintersection with another oppositely facing materials handling vehiclepositioned across the intersection to turn left into the intersection;

FIG. 4H schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have the right ofway when turning left into an intersection with another oppositelyfacing materials handling vehicle positioned across the intersection toturn left into the intersection;

FIG. 4I schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have the right ofway when turning left into an intersection with another oppositelyfacing materials handling vehicle positioned across the intersection tocross straight through the intersection;

FIG. 4J schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have the right ofway when turning left into an intersection with another oppositelyfacing materials handling vehicle positioned across the intersection toturn right into the intersection;

FIG. 4K schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have right of waywhen approaching an intersection behind another materials handlingvehicle;

FIG. 4L schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have right of waywhen approaching an intersection having a stop sign such that themediated materials handling vehicle must make sure that all stop zonesare clear prior to proceeding;

FIG. 4M schematically illustrates the application of local road ruleswhere a mediated materials handling vehicle does not have right of waywhen approaching an intersection having a yield sign such that themediated materials handling vehicle must make sure that all yield zonesare clear prior to proceeding;

FIG. 5A schematically illustrates an example of a simple loopintersection, according to one or more embodiments shown and describedherein;

FIG. 5B schematically illustrates an example of a joining pathsintersection , according to one or more embodiments shown and describedherein;

FIG. 5C schematically illustrates an example of a one way intersection,according to one or more embodiments shown and described herein;

FIG. 5D schematically illustrates an example of a crossing intersection,according to one or more embodiments shown and described herein;

FIG. 5E schematically illustrates an example of an all way stopintersection, according to one or more embodiments shown and describedherein;

FIG. 5F schematically illustrates an example of a shared single lanesegment intersection, according to one or more embodiments shown anddescribed herein;

FIG. 5G schematically illustrates an example of an aisle exitintersection for exit/entry into a single direction path, according toone or more embodiments shown and described herein;

FIG. 5H schematically illustrates an example of another aisle exitintersection for exit/entry into a two lane path, according to one ormore embodiments shown and described herein;

FIG. 5I schematically illustrates an example of a bi-directional trafficin aisle intersection, according to one or more embodiments shown anddescribed herein;

FIG. 6 schematically illustrates a system including a computing devicethat implements the processes of FIGS. 1A, 1B, 3A and/or 3B, accordingto one or more embodiments shown and described herein; and

FIG. 7 schematically illustrates a materials handling vehicle in awarehouse environment and an associated system to implement theprocesses of FIGS. 1A, 1B, 3A and/or 3B, according to one or moreembodiments shown and described herein.

DETAILED DESCRIPTION

The present disclosure provides processes and systems configured toassist with traffic management of materials handling vehicles in awarehouse environment. For example, the present disclosure providestraffic flow solutions at controlled or contention areas such asintersections or contention points in shared warehouse regions to ensurefree flow of traffic within such areas. A controlled area such as anintersection may be defined as an area of contention where access shouldbe limited based on the presence of other materials handling vehicles.Multiple semi-autonomous and/or autonomous materials handling vehiclesmay need to give way to each other, or to manual drivers, to allow freeflowing traffic and prevent deadlock at the contention areas. Contentionareas, such as intersections, may be encoded as part of zones that mayinclude, for example, one or more entry/prompt zones of pre-commissionedintersections.

Materials handling vehicles described herein may interact with otherautomated or semi-automated materials handling vehicles, manually drivenmaterials handling vehicles, non-vehicular obstacles, such as, forexample, loaded or unloaded warehouse pallets, debris, pedestrians, andother obstacles that would potentially obstruct traffic flow in awarehouse environment, and pre-positioned warehouse objects, such as,for example warehouse racking features, warehouse hardware definingwarehouse aisles, or other warehouse infrastructure (arms, lifts, doorsand/or other traffic controls). Material handling vehicles describedherein may be tugger-type vehicles such as tugger automated guidedvehicles, which may be configured to tug a chain of carts, and/or lifttrucks as available from Crown Equipment Corporation such as, forexample, SP Series Order Pickers such as the Crown SP 3500/4500 SeriesOrder Picker and/or TSP Turret Trucks such as one of the TSP 7000 VNATruck Series. The materials handling vehicles described herein mayincorporated automated guidance vehicle (AGV) functionality using, forexample, wire guidance or other guidance features for AGV positioningfunctionality such as radio-frequency identification (RFID) tags. Forexample, RFID tags may be disposed throughout a warehouse environment toact as active or passive transponders communicating with the materialshandling vehicles and/or one or more networks to assist with vehicletracking, navigation, and traffic management through the warehouseenvironment.

In embodiments, an automated or semi-automated vehicle system will bedesigned such that a materials handling vehicle will be configured tostop before colliding with other materials handling vehicles. Vehicletraffic issues with other materials handling vehicles may include delaysand/or deadlocks, which may be classified as a situation requiring amanual operator to resolve. The embodiments described herein provide oneor more implementation processes and systems for traffic management ofmaterials handling vehicles in a warehouse environment to avoid and/orprevent such traffic issues.

In embodiments, a traffic management system comprises a remote or localtraffic management server configured to grant permission to submittedvehicle requests to proceed through an intersection based on clearanceof prior submitted requests and corresponding exit notifications. By wayof example and not as a limitation, and as described in greater detailbelow, a traffic management system comprises control architecturecomprising one or more architecture controllers programmed to: receivethrough a traffic management server a request from a navigation moduleof a mediated vehicle to proceed through an intersection within themultivehicle warehouse; determine whether the traffic management serverhas received one or more prior requests from one or more of theplurality of materials handling vehicles to proceed through theintersection; and determine whether the one or more prior requests toproceed through the intersection comprise corresponding exitnotifications that are indicative of progress through and exit from theintersection in response to a determination that the traffic managementserver has received one or more prior requests to proceed through theintersection. The one or more architecture controllers may further beprogrammed to: transmit through the traffic management server permissionto proceed through the intersection to the navigation module of themediated vehicle in response to a determination that the trafficmanagement server has not received one or more prior requests to proceedthrough the intersection, or in response to the determination that thetraffic management server has received one or more prior requests toproceed through the intersection comprising corresponding exitnotifications.

I. Remotely Mediated Embodiment

In a remotely mediated embodiment, a centralized server is used to trackthe state of contention areas (such as intersections). Each contentionarea may be associated with a unique identifier. When an autonomous orsemi-autonomous materials handling vehicle (such as a truck or forklift)approaches an intersection, the materials handling vehicle may announcethat approach to the server via a reference to the unique identifierassociated with the intersection. The materials handling vehicle mayrequest permission to enter the intersection from the server. If noother materials handling vehicle is in the intersection, the server willgrant permission, and other materials handling vehicles will be deniedand requested to wait until the current materials handling vehicleleaves the intersection. The materials handling vehicle will enter andproceed through the intersection and notify the server when thematerials handling vehicle, including any associated components such asattached carts, is clear of the intersection.

Alternatively, if there are one or more other materials handlingvehicles in the intersection when the materials handling vehiclerequests permission to enter the intersection from the server, theserver sends back a wait request to the materials handling vehicle. Thematerials handling vehicle may re-request permission to enter theintersection after a period of time such as, for example, after between5 seconds to about 10 seconds. If the intersection remains occupied formore than a certain amount of time, such as one minute, then the servermay create an alert indicating that a manual examination of thesituation at the intersection may be needed. A supervisor may then bedispatched to the intersection to clear the intersection state.Information regarding the cleared state may be provided to the server.

The remotely mediated embodiment may be implemented through animplementation process, such as one described in greater detail furtherbelow with respect to FIG. 1A, and may include one or more remoteservers to assist with basic free flow at intersections or contentionpoints to provide deadlock free operation. For example, a failure of theintersection management may lead to a deadlock between multiplematerials handling vehicles and may require manual intervention toresolve. The remotely mediated embodiment may be utilized to assist withpreventing a number of such traffic situations that would arise. Forexample, contention areas such as bi-directional single lane zones andthe like (described in greater detail further below) may be managedthrough the remotely mediated embodiment. Intersection constraintsfollowed by the remotely mediated embodiment (and others embodimentsdescribed herein) may include, for example, a rule to only have a singlematerials handling vehicle allowed in a controlled area at a time and/ora rule to guarantee an exit route from a controlled area for a materialshandling vehicle.

In embodiments, the server may not comprise information regarding thecontrolled area and/or may be configured to learn and store suchinformation (such as an associated unique identifier) based on materialshandling vehicle requests. In embodiments, the server may not have anyglobal path knowledge and/or provide any control of driven path. Theserver may not have knowledge of materials handling vehicles in an areaaround an intersection other than of those materials handling vehiclesthat have communicated with the server and are waiting for access tothat intersection. Further, contention areas, such as intersections, maybe predefined in the site data on board a materials handling vehicle, inthe site data on the server, and/or inferred from materials handlingvehicle communications. For example, a materials handling vehicle mayinitiate communication with the server and convey all information neededto manage the intersection. Thus, when a materials handling vehicle isin the intersection, the materials handling vehicle is not required todepend on another materials handling vehicle moving before the materialshandling vehicle can exit the intersection as the materials handlingvehicle should only have been granted access by the system to a clearedintersection with a guaranteed exit route. The materials handlingvehicle may notify the server when the materials handling vehicle exitsthe intersection.

In some remotely mediated embodiments, an implementation process mayinclude a server tracking a persistent state of all controlled,contention areas (such as intersections), each of which may have aunique identifier. The server may not have information regarding thephysical dimensions of controlled areas and may potentially start withno information regarding controlled areas. The server may be configuredto learn about the controlled areas (such as associated locationinformation, a unique identifier, and the like) based on materialshandling vehicle requests. In the implementation process, a materialshandling vehicle may announce when the materials handling vehicle isapproaching a controlled area through reference to a unique identifierthat is associated with the controlled area and may request permissionto enter from the server. The server may either reply “OK” or “WAIT”depending on area state. If requested to wait, the materials handlingvehicle may re-request after a time period (such as 5 seconds). If an OKreply is received from the server, then the materials handling vehiclemay proceed through the intersection and notify the server when thematerials handling vehicle (and all materials handling vehiclecomponents such as any attached carts) is clear of the controlled area.If the controlled area remains occupied for more than a certain time(such as 1 minute), the server may create an alert providing anotification that a supervisor should be dispatched to manually examinethe situation. The supervisor may be able to manually clear theintersection state from a graphical user interface (GUI) of the server.

Referring to FIG. 1A, for example, an implementation process 100 for aremotely mediated embodiment may comprise a step 102 in which thematerials handling vehicle determines an approach to and approaches acontrolled area such as an entry/prompt zone of a pre-commissionedintersection. Referring to FIG. 2, an example application 250 may beapplied with the implementation process 100 of FIG. 1A. FIG. 2illustrates a mediated materials handling vehicle 400 approaching anintersection zone 258 along the path of an arrow 264. The exampleapplication 250 may further be utilized with respect to animplementation process 200 of FIG. 1B, which is described in greaterdetail further below.

Referring back to FIG. 1A, in a following step 104, the materialshandling vehicle sends a request to proceed through the intersection toa server. Referring again to FIG. 2, the mediated materials handlingvehicle 400 approaches a trigger point 252 at an initial boundary of anentry/prompt zone 254. At the trigger point 252, the mediated materialshandling vehicle 400 sends a request to proceed to the server. In step106 (FIG. 1A), the materials handling vehicle waits at the intersectionand, in step 108, the system determines if the server has received priorrequests. If not, in step 112, the server grants the materials handlingvehicle permission to proceed through the intersection. Thus, the servergrants the materials handling vehicle permission to proceed through theintersection based on a determination that the server has not receivedprior requests.

If, however, the server has received prior requests, the system in step110 determines whether each prior request has a corresponding exitnotification. Thus, based on a determination that the server hasreceived prior requests, the server determines whether each priorrequest has a corresponding exit notification. If so, the server grantsthe materials handling vehicle permission to proceed through theintersection in step 112. Thus, the server grants the materials handlingvehicle permission to proceed through the intersection based on adetermination that each prior request has a corresponding exitnotification.

If not, the materials handling vehicle continues to wait at theintersection in step 106 until either the system determines that theserver does not have any other prior requests in step 108 or that eachprior request has a corresponding exit notification in step 110. Thus,the server does not grant the materials handling vehicle permission toproceed through the intersection such that the materials handlingvehicle continues to wait at the intersection based on a determinationthat each prior request does not have a corresponding exit notification.The materials handling vehicle will continue to wait until a firstdetermination point that the server does not have any prior requests ora second determination point that each prior request has a correspondingexit notification is reached. At either determination point, the servermay then grant the materials handling vehicle permission to proceedthrough the intersection in step 112.

In step 114, the materials handling vehicle proceeds through theintersection when granted permission. Referring to FIG. 2, to proceedpast the point 256 at an opposing end of the entry/prompt zone 254, themediated materials handling vehicle 400 must have received clearance topass from the server. In step 116, the materials handling vehicle sendsan intersection-exit notification to the server. For example, afterreceiving clearance to pass, the mediated materials handling vehicle 400may then pass through the intersection zone 258 to reach an exitnotification point 260 at an initial boundary of an exit zone 262, atwhich point the mediated materials handling vehicle 400 sends theintersection-exist notification to the server.

In embodiments, limitations based on traffic rules may also generallyimply restrictions on how a warehouse environment is laid out andoperated. For example, application of simple traffic rules may only workfor a very narrow aisle (VNA) facility if the VNA facility is laid outand operated in a serpentine fashion.

With respect to the remotely mediated embodiments, a fully coordinatedtraffic management system may utilize one or more servers responsiblefor coordinating a fleet of autonomous materials handling vehicles. Forexample, a large VNA area with a rule based traffic manager would likelyrequire serpentine paths through the aisles, whereas a fully-managedwarehouse may be laid out and operate to allow multiple materialshandling vehicles in an aisle traveling in different directions. Fortugger-type scenarios, this connectivity may enable better performancein congested areas. For manual materials handling vehicles, basicadjustments could be made based on congestion or predicted motion. Theserver in these scenarios may still be able to run smart traffic lights(as described in greater detail below) or give an all clear forintersections for which a materials handling vehicle would otherwiseslow down such that the materials handling vehicle may proceed throughthe intersection without slowing down.

In an embodiment, an implementation process for a remotely mediatedembodiment comprises a step in which a materials handling vehicledetermines an approach to and approaches a controlled area such as anentry/prompt zone of a pre-commissioned intersection. In a followingstep, the materials handling vehicle sends a request to proceed throughthe intersection to a server. The materials handling vehicle waits atthe intersection and the system determines if the server has receivedprior requests. If not, the server grants the materials handling vehiclepermission to proceed through the intersection. If, however, the serverhas received prior requests, the system determines whether each priorrequest has a corresponding exit notification. If so, the server grantsthe materials handling vehicle permission to proceed through theintersection. If not, the materials handling vehicle continues to waitat the intersection until either the system determines that the serverdoes not have any other prior requests or that each prior request has acorresponding exit notification. At either determination point, theserver may then grant the materials handling vehicle permission toproceed through the intersection. The materials handling vehicleproceeds through the intersection when granted permission, and thematerials handling vehicle sends an intersection-exit notification tothe server.

II. Locally Mediated Embodiment

In a locally mediated embodiment, a materials handling vehicle requestsclearance of an intersection through use of a local mediator, ratherthan through a remote request to a central server as implemented in theremotely mediated embodiment described above. In embodiments, the localmediator may be, for example, a smart traffic light with an embeddedcomputer, connected via a short range wireless technology (such aszigbee, Bluetooth, z-wave, and the like).

Referring to FIG. 1B, an implementation process 200 for a locallymediated embodiment may comprise a step 202 in which the materialshandling vehicle determines an approach to and approaches a controlledarea such as an entry/prompt zone of a pre-commissioned intersection.Referring to FIG. 2, the example application 250 may be applied with theimplementation process 200 of FIG. 1B. For example, FIG. 2 illustrates amediated materials handling vehicle 400 that may be using theimplementation process 200 of FIG. 1B approaching an intersection zone258 along the path of an arrow 264.

Referring back to FIG. 1B, in a following step 204, the materialshandling vehicle sends a request to proceed through the intersection toa local mediator as described herein. Referring again to FIG. 2, themediated materials handling vehicle 400 approaches a trigger point 252at an initial boundary of an entry/prompt zone 254. At the trigger point252, the mediated materials handling vehicle 400 sends a request toproceed to the local mediator. In step 206 (FIG. 1B), the materialshandling vehicle waits at the intersection. In step 208, the systemdetermines if the local mediator has received prior requests. If not, instep 212, the local mediator grants the materials handling vehiclepermission to proceed through the intersection. Thus, the local mediatorgrants the materials handling vehicle permission to proceed through theintersection based on a determination that the local mediator has notreceived prior requests.

If, however, the local mediator has received prior requests, the systemin step 210 determines whether each prior request has a correspondingexit notification. Thus, based on a determination that the localmediator has received prior requests, the local mediator determineswhether each prior request has a corresponding exit notification. If so,the local mediator grants the materials handling vehicle permission toproceed through the intersection in step 212. Thus, the local mediatorgrants the materials handling vehicle permission to proceed through theintersection based on a determination that each prior request has acorresponding exit notification.

If not, the materials handling vehicle continues to wait at theintersection in step 206 until either the system determines that thelocal mediator does not have any other prior requests in step 208 orthat each prior request has a corresponding exit notification in step210. Thus, the local mediator does not grant the materials handlingvehicle permission to proceed through the intersection such that thematerials handling vehicle continues to wait at the intersection basedon a determination that each prior request does not have a correspondingexit notification. The materials handling vehicle will continue to waituntil a first determination point that the local mediator does not haveany prior requests or a second determination point that each priorrequest has a corresponding exit notification is reached. At eitherdetermination point, the local mediator may then grant the materialshandling vehicle permission to proceed through the intersection in step212.

In step 214, the materials handling vehicle proceeds through theintersection when granted permission. Referring to FIG. 2, to proceedpast the point 256 at an opposing end of the entry/prompt zone 254, themediated materials handling vehicle 400 must have received clearance topass from the local mediator. In step 216, the materials handlingvehicle sends an intersection-exit notification to the local mediator.For example, after receiving clearance to pass, the mediated materialshandling vehicle 400 may then pass through the intersection zone 258 toreach an exit notification point 260 at an initial boundary of an exitzone 262, at which point the mediated materials handling vehicle 400sends an intersection-exist notification to the local mediator.

In an embodiment, an implementation process for a locally mediatedembodiment comprises a step in which a materials handling vehicledetermines an approach to and approaches a controlled area such as anentry/prompt zone of a pre-commissioned intersection. In a followingstep, the materials handling vehicle sends a request to proceed throughthe intersection to a local mediator as described herein. The materialshandling vehicle waits at the intersection. The system determines if thelocal mediator has received prior requests. If not, the local mediatorgrants the materials handling vehicle permission to proceed through theintersection. If, however, the local mediator has received priorrequests, the system determines whether each prior request has acorresponding exit notification. If so, the server grants the materialshandling vehicle permission to proceed through the intersection. If not,the materials handling vehicle continues to wait at the intersectionuntil either the system determines that the local mediator does not haveany other prior requests or that each prior request has a correspondingexit notification. At either determination point, the local mediator maythen grant the materials handling vehicle permission to proceed throughthe intersection. The materials handling vehicle proceeds through theintersection when granted permission, and the materials handling vehiclesends an intersection-exit notification to the local mediator.

III. Vehicle-Sensor Mediated Embodiment

In yet another embodiment, materials handling vehicles feature localsensor data (such as laser scan data) to determine when to proceed intoan intersection. The determination may be based on local obstacledetection and traffic rules. When the materials handling vehicleapproaches the intersection, zone data will determine which of the oneor more zones (i.e., zone(s)) defining a give way region of anintersection must be clear before the materials handling vehicle mayenter the intersection. A priority ordering may be created and used thatis similar to traditional local road rules (e.g., a yield would requirethat the left (or right) zones of the intersection that define the giveway region are clear before entering the intersection, whereas a stopwould require that all zones of the intersection that define the giveway region are clear).

The give way region particular to an intersection following road rulesassociated with the intersection may be constructed from intersectionzone data. The materials handling vehicle then uses sensor data (such aslaser scan data generated through a sensor comprising a 2D laserscanner, for example) to ensure these regions are clear before enteringthe intersection. Such a laser based approach may allow fordecentralized implementation, as well as detection of manually drivenmaterials handling vehicles. Obstacle detection through the laserscanner may scan an area surrounding a materials handling vehicle as itproceeds through an intersection, such as materials handling vehiclesentered from an opposite side of the intersection. In embodiments, theintersection may have a reduced speed limit such that materials handlingvehicles proceeding through the intersection adjust speed to be at orbelow the reduced speed limit.

In embodiments, a materials handling vehicle may be able to determine apresence of another materials handling vehicle in an intersection butnot the state of the other materials handling vehicle in theintersection, and the materials handling vehicle may not be able toaffect the state of other materials handling vehicles. In embodiments,the materials handling vehicle and/or local network may not have priorknowledge of materials handling vehicle locations. Obstacle detectionmay be implemented in a system running on materials handling vehiclessuch that the system is configured to slow a respective materialshandling vehicle upon such obstacle detection before any laser safetyfields are infringed, which minimizes human intervention and emergencystops.

Vehicle-sensor mediated embodiments may run online with respect to asystem on the materials handling vehicle, may feature real timeperformance, and may be deployed through a local network within a shortdistance range of an intersection. Intersection constraints followed bythe vehicle-sensor mediated embodiment may include, for example, a ruleto only have a single materials handling vehicle allowed in a controlledarea at a time and/or a rule to guarantee an exit route from acontrolled area for a materials handling vehicle.

Vehicle-sensor mediated embodiments may be applied to autonomous,semi-autonomous, and/or manual materials handling vehicles that followthe same rule set. In vehicle-sensor mediated embodiments, the materialshandling vehicle is responsible for local isolated resolution of rightof way. Obstacle detection may be used to identify other materialshandling vehicles at the intersection point, and then simple local roadrules, such as “give way to the right” or “give way to all traffic” maybe used to decide behavior. In embodiments, the implementation may be apurely local implementation that features obstacle detection andpotentially features an accurate map of fixed infrastructure obstacles.One or more of the materials handling vehicles may be configured tostore one or more warehouse maps including, for example, informationregarding locations of such fixed obstacles in the warehouseenvironment.

Continuing with the vehicle-sensor mediated embodiments, in animplementation process, such as one described below in greater detailwith respect to FIG. 3A, a materials handling vehicle may enter anintersection by determining an approach to, approaching, and entering anintersection-approach zone. The materials handling vehicle may establishmap positions of the intersection and other approach zones. As anexample and not by way of limitation, commissioning tools for a zone mapor rule set may have local road rules (e.g., giving way to theright/left) encoded in order to assist in construction of the map. Inembodiments, the materials handling vehicle may plan a stop point andbegin slowing when approach the stop point. At the stop point, thematerials handling vehicle may check if the zones are clear throughobstacle detection conducted through the laser scanner. If the zones areclear, the materials handling vehicle may proceed up to the speed limitassociated with the intersection and/or set by materials handlingvehicle rules or local road rules. If the approach zones are infringedsuch that the one or more zones defining a give way region are notclear, the materials handling vehicle may apply local road rules withrespect to the give way region of the intersection. In embodiments, ifthe materials handling vehicle has a right of way, the materialshandling vehicle may proceed into the intersection up to theintersection speed limit. If the field of view of the laser scanner isinfringed and detects an obstacle, or if the laser scanner generates anobstructed view, the materials handling vehicle may stop at apredetermined point and wait for an intersection zone to be clear beforereapplying the local road rules.

Referring to FIG. 3A, an implementation process 300 for a vehicle-sensormediated embodiment may comprise a step 302 in which the materialshandling vehicle determines an approach to and approaches a controlledarea such as an entry/prompt zone of a pre-commissioned intersection.Referring to FIG. 3C, an example application 270A may be applied withthe implementation process 300 of FIG. 3A. FIG. 3C illustrates amediated materials handling vehicle 400 approaching an intersection zonealong the path of an arrow 282A. Similarly, referring to FIGS. 3D, 3E,and 3F, example applications 270B, 270C, and 270D may be applied withthe implementation process 300 of FIG. 3A, where FIGS. 3D, 3E, and 3Frespectively illustrate a mediated materials handling vehicle 400approaching an intersection zone along the path of an arrow 282B, 282C,and 282D associated with respective path projected headings 280B, 280C,and 280D. As a non-limiting example, FIG. 3C illustrates a mediatedmaterials handling vehicle 400 approaching an intersection zone alongthe path of an arrow 282A associated with straight cross path projectedheading 280A. FIG. 3D illustrates a mediated materials handling vehicle400 approaching an intersection zone along the path of an arrow 282Bassociated with right turn path projected heading 280B. FIG. 3Eillustrates a mediated materials handling vehicle 400 approaching anintersection zone along the path of an arrow 282C associated withstraight cross path projected heading 280C. FIG. 3F illustrates amediated materials handling vehicle 400 approaching an intersection zonealong the path of an arrow 282D associated with right turn pathprojected heading 280D.

Referring back to FIG. 3A, in a following step 304, road rules may beapplied to the intersection as described herein from zone data todetermine the one or more zones (i.e., zone(s)) defining a give wayregion to clear in the intersection. As an example, and as describedabove, a yield would require that the left (or right) zones of theintersection that define the give way region are clear before enteringthe intersection. However, a stop would require that all zones of theintersection that define the give way region are clear.

Thus, in the next step 306, the materials handling vehicle laser-scansthe give way region. For example, referring to FIG. 3C, the mediatedmaterials handling vehicle 400 approaches a trigger point 272 of aninitial boundary of an entry zone 274, with an exit boundary of theentry zone 274 defined by an entry zone exit point 276, scans a give wayregion 278A, applies obstacle detection rules to a path 280A along thearrow 282A in the give way region 278A, and only proceeds into the giveway region 278A of the intersection if the give way region 278A isdetermined to be clear.

For example, after such scanning, in step 308 (FIG. 3A), a determinationis made as to whether the zone(s) defining the give way region containanother materials handling vehicle such that the zone(s) are not clear.If so, the materials handling vehicle proceeds to continue to scan thegive way region 278A in step 306 and wait until the zone(s) are clear.Thus, materials handling vehicle proceeds to continue to scan the giveway region based on a determination that the zone(s) defining the giveway region contain another materials handling vehicle such that thezone(s) are not clear. If not, and the zone(s) are clear, then in step310 the materials handling vehicle proceeds through the intersection.Thus, the materials handling vehicle proceeds through the intersectionbased on a determination that the zone(s) defining the give way region278A do not contain another materials handling vehicle such that thezone(s) are clear.

Some embodiments may leverage zones to define intersection and approachzones. Further, some embodiments may support local road rules comprisingleft and right hand give way rules, and may include a hierarchy of stopand give way rules. Further, in some embodiments, a materials handlingvehicle may stop for another materials handling vehicle that cannot stopin time.

Referring to FIG. 3B, an implementation process 320 may initiate with astep 322 to operate the materials handling vehicle and in step 324determine whether the materials handling vehicle is approaching or at apotentially contested intersection. Referring to FIG. 3C and FIG. 7, theexample application 270 may be applied with the implementation process320 of FIG. 3B. As described above, FIG. 3C illustrates a materialshandling vehicle 400 approaching an intersection zone including apotentially contested intersection 271A along the path of an arrow 282A.Referring to FIG. 7, the materials handling vehicle 400 is configured tonavigate a vehicle transit surface 12 in a warehouse environment 10. Thematerials handling vehicle 400 includes a vehicle body 11, a pluralityof vehicle wheels 24 supporting the vehicle body 11, a traction controlunit 34, a braking system 36, and a steering assembly 38, eachoperatively coupled to one or more of the plurality of vehicle wheels24, an obstacle detection subsystem 40, and a navigation subsystem 42.The traction control unit 34, the braking system 36, and the steeringassembly 38 may each operatively coupled to one or more of the pluralityof vehicle wheels 24 through operator controls 26, for example. Thetraction control unit 34, the braking system 36, the steering assembly38, the obstacle detection subsystem 40, and the navigation subsystem 42may reside on a local terminal 32 of the materials handling vehicle 400.

Referring to FIGS. 3B-3F and FIG. 7, and as set forth in step 324 ofFIG. 3B, the navigation subsystem 42 is configured to cooperate with thetraction control unit 34, the braking system 36, the steering assembly38, and the obstacle detection subsystem 40 to determine whether thematerials handling vehicle 400 is approaching, or has arrived at, or isotherwise in the vicinity of a potentially contested intersection 271A,271B. In embodiments, the navigation subsystem 42 is configured tocooperate with the traction control unit 34, the braking system 36, thesteering assembly 38, and the obstacle detection subsystem 40 through acommunicative coupling 46.

The navigation subsystem 42 is configured to determine whether thematerials handling vehicle 400 is approaching, or has arrived at, apotentially contested intersection 271A, 271B by establishing orrecognizing an entry zone 274 associated with the potentially contestedintersection 271A, 271B, and indicating a presence of the materialshandling vehicle 400 in the entry zone 274. The navigation subsystem 42may establish the entry zone 274 as a virtual boundary in the warehouseenvironment 10. Alternatively, the navigation subsystem 42 may establishthe entry zone 274 as a literal entry zone defined by boundary elementsin the warehouse environment 10. As a non-limiting example, one or moreRFID tags arranged near the intersection 271A, 271B, at the end of anaisle. In embodiments, the materials handling vehicle 400 may includehardware configured to establish or recognize the entry zone 274associated with the potentially contested intersection 271A, 271B, whichhardware may include a sensor array including at least one of a lasersensor, a radar sensor, and an image sensor.

The navigation subsystem 42 may be configured to determine whether thematerials handling vehicle 400 is approaching, or has arrived at, apotentially contested intersection 271A, 271B by interacting with alocalization subsystem to determine a position and heading of thematerials handling vehicle 400 relative to the potentially contestedintersection 271A, 271B. The localization subsystem may be configured toreceive measurement data from one or more sensors of the materialshandling vehicle 400 and determine the position and heading of thematerials handling vehicle 400 in the warehouse environment 10 based onthe measurement data. The localization subsystem is configured tointeract with one or more warehouse maps 730, described in greaterdetail below, to determine the position and heading of the potentiallycontested intersection 271A, 271B relative to the materials handlingvehicle 400. In an embodiment, the localization subsystem resides on thematerials handling vehicle 400. In an alternative embodiment, thelocalization subsystem is remote from the materials handling vehicle400.

The navigation subsystem 42 may further include one or moreenvironmental sensors configured to capture data indicative of a headingand position of the materials handling vehicle 400 relative to thevehicle transit surface 12. The one or more environmental sensors maycomprise one or more image sensors disposed to face an upward directionto detect upwardly disposed features 14 in the warehouse environment 10.For example, the image sensors may be one or more cameras 20 disposed toface the upward direction, and the upwardly disposed features compriseone or more lights, one or more skylights 16, or both. Additionally oralternatively, the one or more environmental sensors may be one or moreimage sensors disposed to face a lateral direction in the warehouseenvironment 10 to detect laterally disposed features in the warehouseenvironment 10. Additionally or alternatively, the one or moreenvironmental sensors may be a tag reader configured to read one or moreRFID tags disposed in the warehouse environment 10. The one or moreenvironmental sensors may be hardware on the materials handling vehicle400 comprising a sensor array, the sensor array comprising at least oneof a laser sensor, a radar sensor, and an image sensor.

The navigation subsystem 42 may comprise one or more environmentalsensors and an environmental database. In embodiments, the environmentalsensors are configured to capture data indicative of a position of thematerials handling vehicle 400 relative to the vehicle transit surface12 in the warehouse environment 10. Further, the environmental databasemay reside on or be remote from the materials handling vehicle 400 andmay comprise stored data indicative of the one or more intersections,the vehicle transit surface 12, or both. The navigation subsystem 42 maybe configured to enable at least partially automated navigation of thematerials handling vehicle along the vehicle transit surface 12utilizing the captured data and the stored data. For example, and not byway of limitation, it is contemplated that the navigation subsystem 42,the localization system, or both may utilize a stored warehouse map 730and captured images of ceiling lights or skylights 16 to enablenavigation, localization, or both, as is disclosed in U.S. Pat. No.9,174,830 issued on Nov. 3, 2015, (CRNZ 0053 PA), U.S. Pat. No.9,340,399 issued on May 17, 2016 (docket no. CRNZ 0053 NA), U.S. Pat.No. 9,349,181 issued on May 24, 2016 (docket no. CRNZ 0052 PA), U.S.Pat. No. 9,958,873 issued May 1, 2018 (docket no. INRO 0009 NA), andother similar patents and patent publications. It is furthercontemplated that the navigation subsystem 42, the localizationsubsystem, or both may utilize a stored warehouse map 730 and a taglayout disposed on the vehicle transit surface 12 as disclosed in U.S.Pat. No. 9,811,088 issued on Nov. 7, 2017 (CRO 0056 PA), and othersimilar patents and patent publications. Additional suitableenvironmental sensors include, but are not limited to, inertial sensors,lasers, antennae for reading RFID tags, buried wires, WiFi signals, orradio signals, global positioning system (GPS) sensors, globalnavigation satellite system (GNSS) sensors, or combinations thereof.

The navigation subsystem 42 is further configured to cooperate with thetraction control unit 34, the braking system 36, the steering assembly38, and the obstacle detection subsystem 40 to associate pre-positionedwarehouse object data derived from a database of pre-positionedwarehouse objects 30 in the warehouse environment 10 with thepotentially contested intersection 271A, 271B, as set forth in step 326of FIG. 3B. The associated pre-positioned warehouse object data mayrepresent warehouse racking features, warehouse hardware definingwarehouse aisles, other warehouse infrastructure, or a combinationthereof. The database may be “dynamic,” i.e., the associatedpre-positioned object data within the database as a dynamic database maybe updated when the aforementioned warehouse infrastructure change withrespect to the warehouse environment 10. In an embodiment, associatingpre-positioned warehouse object data derived from the database ofpre-positioned warehouse objects 30 in the warehouse environment 10 withthe potentially contested intersection 271A, 271B may include updatinglocations of one or more pre-positioned warehouse objects that changewith respect to the warehouse environment in the database ofpre-positioned warehouse objects. As a non-limiting example, thedatabase of pre-positioned warehouse objects may be dynamic and thedatabase of pre-positioned objects may be updated to represent locationchanges of one or more pre-positioned warehouse objects with respect tothe warehouse environment, additions to or deletion of one or morepre-positioned warehouse objects in the warehouse environment, or acombination thereof. The database of pre-positioned warehouse objects 30may be stored at a location that is remote from the materials handlingvehicle 400, such as at a remote terminal 28 remote from the materialshandling vehicle 400. The materials handling vehicle 400 comprisescommunications hardware configured to access the remote database ofpre-positioned warehouse objects 30. Alternatively, the database ofpre-positioned warehouse objects 30 may reside on the materials handlingvehicle 400.

In an embodiment, a system may include the remote terminal 28, thematerials handling vehicle 400 configured to navigate the vehicletransit surface 12 in the warehouse environment 10, and the database ofpre-positioned warehouse objects 30 in the warehouse environment,wherein the navigation subsystem is configured to communicate with theremote terminal 28. The remote terminal 28 may be configured to maintainthe database of pre-positioned warehouse objects 30.

The navigation subsystem 42 is further configured to cooperate with thetraction control unit 34, the braking system 36, the steering assembly38, and the obstacle detection subsystem 40 to associate a set of roadrules 44 with the potentially contested intersection, as set forth instep 328 of FIG. 3B, and associate obstacle data derived from theobstacle detection subsystem 40 with the potentially contestedintersection 271A, 271B, as set forth in step 330 of FIG. 3B. In anembodiment, the navigation subsystem 42 is further configured todetermine whether the obstacle data derived from the obstacle detectionsubsystem 40 correlates with a competing materials handling vehicle 400or a non-vehicular obstacle. The navigation subsystem 42 may be furtherconfigured to determine whether at least a portion of the obstacle dataderived from the obstacle detection subsystem 40 correlates with acompeting materials handling vehicle 400. Alternatively, the navigationsubsystem 42 is further configured to determine whether the obstacledata derived from the obstacle detection subsystem 40 correlates with apre-positioned warehouse object from the database of pre-positionedwarehouse objects 30.

In embodiments, the obstacle detection subsystem 40 may include anobstacle scanning device, an imaging system, a range finder, a radarsensor, a ladar sensor, a laser scanner, or combinations thereof. Theobstacle detection subsystem 40 may utilize detection hardware operatingin the infrared or visible wavelength ranges.

The navigation subsystem 42 is further configured to cooperate with thetraction control unit 34, the braking system 36, the steering assembly38, and the obstacle detection subsystem 40 to navigate the materialshandling vehicle 400 through the potentially contested intersection271A, 271B utilizing warehouse navigation maneuvers in combination withthe associated set of road rules 44, obstacle avoidance maneuvers, orboth, as set forth in step 332 of FIG. 3B. The warehouse navigationmaneuvers may comprise conventional, or yet to be developed, maneuversfor successfully navigating a materials handling vehicle through awarehouse environment, such as, for example, navigation maneuversdescribed in U.S. Pat. No. 9,174,830 issued on Nov. 3, 2015, (CRNZ 0053PA), U.S. Pat. No. 9,340,399 issued on May 17, 2016 (docket no. CRNZ0053 NA), and other similar patents and patent publications. Thewarehouse navigation maneuvers account for the associated pre-positionedwarehouse object data, such as, for example, warehouse racking features,warehouse hardware defining warehouse aisles, or other warehouseinfrastructure. The obstacle avoidance maneuvers may compriseconventional, or yet to be developed, maneuvers for successfullynavigating a materials handling vehicle around non-vehicular obstaclesin a warehouse environment, such as, for example, obstacle avoidancemaneuvers described in U.S. Pat. No. 9,958,873 issued May 1, 2018(docket no. INRO 0009 NA), and other similar patents and patentpublications. The obstacle avoidance maneuvers account for obstacle dataderived from the obstacle detection subsystem 40, such as, for example,loaded or unloaded warehouse pallets, debris, and other obstacles thatwould potentially obstruct traffic flow in a warehouse environment.

In an embodiment, the navigation subsystem 42 is further configured tonavigate the materials handling vehicle 400 through the potentiallycontested intersection 271A, 271B utilizing the warehouse navigationmaneuvers and either the associated set of road rules 44 or the obstacleavoidance maneuvers, depending on whether the obstacle data correlateswith a competing materials handling vehicle 400 or a non-vehicularobstacle. As a non-limiting example, the navigation subsystem 42 isfurther configured to navigate the materials handling vehicle 400through the potentially contested intersection 271A, 271B utilizing thewarehouse navigation maneuvers and the associated set of road rules 44,when the obstacle data correlates with a competing materials handlingvehicle 400. Further, the navigation subsystem 42 is further configuredto navigate the materials handling vehicle through the potentiallycontested intersection 271A, 271B utilizing the warehouse navigationmaneuvers and the obstacle avoidance maneuvers, when the obstacle datacorrelates with a non-vehicular obstacle.

The associated set of road rules 44 may account for vehicle positioningrelative to the potentially contested intersection 271A, 271B,intersection characteristics defining the potentially contestedintersection 271A, 271B, or both. By way of example, and not has alimitation, the associated set of road rules accounts for intersectioncharacteristics defining the potentially contested intersection 271A,271B.

In another embodiment, the navigation subsystem 42 is further configuredto navigate the materials handling vehicle 400 through the potentiallycontested intersection 271A, 271B utilizing the warehouse navigationmaneuvers when the obstacle data correlates with a pre-positionedwarehouse object.

Referring to FIGS. 3C-3F, the navigation subsystem 42 may further beconfigured to define a give way region 278A, 278B, 278C, 278D associatedwith the potentially contested intersection 271A, 271B. Referring toFIGS. 3C-3D, each give way region 278A, 278B is associated with thepotentially contested intersection 271A. Referring to FIGS. 3E-3F, eachgive way region 278C, 278D is associated with the potentially contestedintersection 271B. The give way region 278A, 278B, 278C, 278D may be afunction of an intersection type associated with the potentiallycontested intersection 271A, 271B and a projected vehicle heading 282A,282B, 282C, 282D associated with the materials handling vehicle 400,relative to the potentially contested intersection 271A, 271B. Referringto FIGS. 3C-3D, as a non-limiting example, the respective give wayregion 278A, 278B may be a function of an intersection type associatedwith the potentially contested intersection 271A and a respectiveprojected vehicle heading 282A, 282B, associated with the materialshandling vehicle 400, relative to the potentially contested intersection271A. Referring to FIGS. 3E-3F, as a non-limiting example, therespective give way region 278C, 278D may be a function of anintersection type associated with the potentially contested intersection271B and a respective projected vehicle heading 282C, 282D associatedwith the materials handling vehicle 400, relative to the potentiallycontested intersection 271B.

Referring to FIGS. 3C-3F and 7, the navigation subsystem 42 may furtherbe configured to limit the set of road rules 44 associated with thepotentially contested intersection 271A, 271B by conforming the set ofroad rules 44 to the defined give way region 278A, 278B, 278C, 278D. Thenavigation subsystem 42 may further be configured to navigate thematerials handling vehicle 400 through the potentially contestedintersection 271A, 271B utilizing the warehouse navigation maneuvers andthe conformed set of road rules 44 when the obstacle data correlateswith a competing materials handling vehicle 400. Additionally oralternatively, the navigation subsystem 42 may further be configured tolimit the obstacle data associated with the potentially contestedintersection 271A, 271B by conforming the obstacle data to the definedgive way region 278A, 278B, 278C, 278D, and navigate the materialshandling vehicle 400 through the potentially contested intersection271A, 271B utilizing the warehouse navigation maneuvers, the obstacleavoidance maneuvers, and the conformed obstacle data, when the obstacledata correlates with a non-vehicular obstacle.

In an embodiment, an implementation process for a materials handlingvehicle-sensor mediated embodiment comprises a step in which a materialshandling vehicle determines an approach to and approaches a controlledarea such as an entry/prompt zone of a pre-commissioned intersection. Ina following step, road rules are applied to the intersection asdescribed herein from zone data to determine the one or more zones(i.e., zone(s)) defining a give way region to clear in the intersection.In a next step, the materials handling vehicle laser-scans the give wayregion. After such scanning, a determination is made as to whether thezone(s) defining the give way region contain another materials handlingvehicle such that the zone(s) are not clear. If so, the materialshandling vehicle proceeds to continue to scan the give way region andwait until the zone(s) are clear. If not, and the zone(s) are clear,then the materials handling vehicle proceeds through the intersection.

Embodiments may feature further additional or alternative mediatedintersections, such as local network based peer to peer mediation and/ora smart traffic light type of solution, for example. This would allowfor sites that feature more complex intersections such as all way stop,or shared single lanes. Some form of connectivity may be utilized atmediation points, which could be a direct local link, may utilize a band(that is not, for example, 2.4 GHz such that a standard wirelessfidelity (“wi-fi”) system operating on the 2.4 GHz band in the warehouseenvironment is not utilized or interrupted). In embodiments, animplementation of connectivity at mediation points may use visualindication and image recognition and/or or an active RFID pill.

In peer to peer mediated embodiments, vehicle to vehicle communicationmay be used to negotiate intersection behavior. A type of peer to peertransceiver (such as zigbee, Bluetooth, wifi-direct, UWB, and the like)may be used to identify other materials handling vehicles in the area.Such a peer to peer mediated embodiment may allow for intent to beshared between materials handling vehicles, but may still require somesort of static rule set to negotiate priority between materials handlingvehicle movement (such as fixed priority for certain materials handlingvehicles, priority based on intent or time waiting, and the like).

The remote, local, and/or vehicle-sensor mediated embodiments may bescalable to support any number of autonomous and/or manual materialshandling vehicles. In order to improve interactions with manual drivers,the remote, local, and/or vehicle-sensor mediated embodiments abovecould be combined with a smart traffic light system to indicateintersection state. For example, a smart traffic light system maycomprise a set of physical lights configured to indicate to manualdrivers when they should proceed through the intersection such thatmanual drivers are provided with control options.

Some embodiments may feature infrastructure-based intersectionmediation, where a piece of infrastructure such as a smart traffic lightmay mediate the intersection. In embodiments, implementation may utilizeexternal infrastructure, such as a physical smart traffic light, avirtual traffic light run on a server, smart RFID pills disposed on orwithin a warehouse floor or other intersection locations, for example,and the like. A materials handling vehicle mounted display could also beused to indicate this information with respect to manual materialshandling vehicles that comprise had suitable connectivity and displaysystems.

IV. Application of Local Road Rules

In embodiments that only use standalone local road rules, one or moreonboard lasers may be used for traffic detection and basic positionallocal road rules implemented. This may allow for simple loops, joiningpaths, one way intersections, single lane aisles and pedestriancrossings, etc., and no server or network access may be needed in thistype of embodiment.

FIGS. 4A-4M illustrate different examples of the application of localroad rules to an intersection. For example, typical rules for right-sidedriving may be applied. Cross-hatching in FIGS. 4A-4M is indicative ofone or more scanned and active give way zones to which to apply drivingrules as described below. Further, a materials handling vehicle having aright of way R is indicated in FIGS. 4A-4M, as described in greaterdetail below.

FIG. 4A illustrates the application of local road rules where a mediatedmaterials handling vehicle 400 approaches a clear intersection and hasthe right of way R. For example, as illustrated in FIG. 4A, if amediated materials handling vehicle 400 approaches or has approached aclear intersection, in which the lanes of the other approach zones ofthe intersection are clear, the mediated materials handling vehicle 400may be instructed to proceed through the intersection in any direction(straight through or turning right or left).

However, if the mediated materials handling vehicle 400 has approachedan intersection that includes another materials handling vehicle 402 toleft of the mediated materials handling vehicle 400, i.e., in the leftapproach zone, and has a heading to cross through or turn within theintersection, as illustrated in FIG. 4B, the mediated materials handlingvehicle 400 may be instructed to wait for the other materials handlingvehicle 402 to cross and clear the intersection. Thus, FIG. 4B setsforth the application of local road rules where a mediated materialshandling vehicle 400 does not have the right of way R when approachingan intersection that includes another materials handling vehicle in theleft approach zone. Rather, the other materials handling vehicle 402 hasthe right of way R.

FIG. 4C illustrates the application of local road rules where a mediatedmaterials handling vehicle 400 does not have the right of way R whenapproaching an intersection with an obstacle blocking a field of view ofa sensor disposed on the mediated materials handling vehicle 400 withrespect to a left approach zone. For example, with a vehicle-sensormediated embodiment and referring to FIG. 4C, a mediated materialshandling vehicle 400 may approach an intersection at which an obstacle404 blocks the materials handling vehicle sensor's field of view withrespect to the left approach zone. The mediated materials handlingvehicle 400 may be instructed to slow to a stop-and-scan area to be ableto detect the obstacle 404 and proceed through an implementation processwhere the mediated materials handling vehicle 400 would need to verifythat the intersection is clear before proceeding through theintersection.

FIG. 4D illustrates the application of local road rules where a mediatedmaterials handling vehicle 400 has the right of way R when approachingan intersection with another materials handling vehicle 406 positionedat the intersection in a right approach zone of the intersection, to theright the of mediated materials handling vehicle 400. The othermaterials handling vehicle 406 may have a heading to cross through, orturn within, the intersection. FIG. 4E sets forth the application oflocal road rules where a mediated materials handling vehicle 400 has theright of way R when approaching an intersection with an obstacle 408blocking a field of view of a sensor disposed on the mediated materialshandling vehicle 400 with respect to a right approach zone of theintersection. In either scenario of FIGS. 4D-4E, the local road rulesmay provide that the mediated materials handling vehicle 400 has theright of way R, and the mediated materials handling vehicle 400 isinstructed by the system to proceed through and/or turn within theintersection.

FIG. 4F illustrates a scenario where a mediated materials handlingvehicle 400 has the right of way R when crossing straight through anintersection with another oppositely facing materials handling vehicle410 positioned across the intersection to cross straight through theintersection. FIG. 4G illustrates another scenario where a mediatedmaterials handling vehicle 400 has the right of way R when crossingstraight through an intersection with another oppositely facingmaterials handling vehicle 410 positioned across the intersection toturn left into the intersection. In either scenario of FIGS. 4F-4G, themediated materials handling vehicle 400 has the right of way R and isinstructed to proceed through the intersection at an appropriate speed.Further, in the scenario of FIG. 4G, the other materials handlingvehicle 410 will have to give way to and wait for the mediated materialshandling vehicle 400 to proceed through the intersection.

FIGS. 4H-4J illustrate the application of local road rules where amediated materials handling vehicle 400 does not have the right of way Rwhen turning left into an intersection with another oppositely facingmaterials handling vehicle 410 positioned across the intersection. InFIG. 4H, the other materials handling vehicle 410 has a heading to takea right turn through the intersection. In FIG. 4I, the other materialshandling vehicle 410 has a heading to cross through the intersection. InFIG. 4J, the other materials handling vehicle 410 has a heading to takea left turn through the intersection. In any of these scenarios of FIGS.4H-4J, the mediated materials handling vehicle 400 is to give way to theother materials handling vehicle 410 that will have the right of way Rto avoid potential deadlock and/or collision.

FIG. 4K illustrates the application of local road rules where a mediatedmaterials handling vehicle 400 does not have right of way R whenapproaching an intersection behind another materials handling vehicle412. The mediated materials handling vehicle 400 may be instructed touse a laser scanner to detect the other materials handling vehicle 412in front of the mediated materials handling vehicle 400 as the mediatedmaterials handling vehicle 400 approaches the intersection. The mediatedmaterials handling vehicle 400 may be instructed to wait until the othermaterials handling vehicle 412, which has the right of way R, clears theintersection, and then may need to re-apply road rules prior toproceeding through the intersection.

FIG. 4L illustrates the application of local road rules where a mediatedmaterials handling vehicle 400 does not have right of way R whenapproaching an intersection having a stop sign. The mediated materialshandling vehicle 400 may be instructed to stop and give way to allapproach zones not affected by a stop sign. For example, stop zones mayinclude right approach zones, left approach zones, and crossing zones.For intersections with multiple stop signs, local road rules may beapplied to determine give way patterns based on order of approach toeach stop sign. For example, a materials handling vehicle that is secondto stop at a second stop sign gives way to a materials handling vehiclethat is first to stop at a first stop sign.

FIG. 4M illustrates the application of local road rules where a mediatedmaterials handling vehicle does not have right of way R when approachingan intersection having a yield sign. The mediated materials handlingvehicle 400 will be instructed to yield and give way to right and leftapproach zones (i.e., the yield zones), for example.

V. Types of Intersections and System Requirements

FIGS. 5A-5I illustrate various additional types of intersections thatmay be encountered by a materials handling vehicle and are describedbelow with respect to their associated requirements. Subtle variationsof these intersections may exist, such as where congestion may occurthat turns a relatively simple intersection into a more complex one. Forexample, a tail of a queue of materials handling vehicles waiting at onepoint may interfere with traffic leaving that point in a differentdirection, increasing the complexity of the intersection.

Referring to FIG. 5A, a simple loop intersection 500 is illustrated. Ano passing rule is assumed and the only materials handling vehicleinteraction that occurs includes that a following materials handlingvehicle may need to slow down for a materials handling vehiclepositioned in front of the following materials handling vehicle.

Referring to FIG. 5B, a joining paths intersection 502 is illustrated. Asingle direction joining path enters and joins with a traffic lane thatincludes existing traffic. A mediated materials handling vehicle 400 (asillustrated in FIGS. 4A-4M, for example) that may be on the joining pathand entering the lane with existing traffic is instructed to wait for aclear section of the traffic lane with prior to merging into the trafficlane.

Referring to FIG. 5C, a one way intersection 504 is illustrated thatcomprises a pair of cross one-way routes. Simply give way local roadrules may be applied to this type of intersection. For example, amediated materials handling vehicle 400 may be expected to pause at thecross to allow traffic to proceed based on the applied local road rules.

Referring to FIG. 5D, a crossing intersection 506 is illustrated such asa pedestrian or other crossing 508 that acts as a section of a path atwhich a mediated materials handling vehicle 400 is expected to pause toallow other traffic to proceed, similar to the one way intersection 504.

Referring to FIG. 5E, an all way stop intersection 510 comprises a morecomplex intersection including multiple two lane routes that intersect.Local road rules as described herein may be applied to these types ofintersections, and/or rules applying first in/first out conventions maybe applied.

Referring to FIG. 5F, a shared single lane segment intersection 512comprises a shared single lane that carries bi-directional traffic suchthat it is possible for two materials handling vehicles to deadlock byfacing each other along the central, bi-directional segment 514. Such apath may occur along long corridors, elevators, pinch points, and thelike. In embodiments, local information may not be sufficient to resolvesuch situations and traffic signals may need to be employed that arecoordinated at each end 516, 518 of the bi-directional segment 514. Suchtraffic signals may employ, for example, a first-come/first serve ruleswith respect to usage of the bi-directional segment 514 or a green “go”signal for a predetermined period of time that switches between the ends516, 518 of the bi-directional segment 514.

Referring to FIGS. 5G-5H, alternative embodiments of an aisle exitintersection 520A, 520B are illustrated. For example, exiting orentering a single direction aisle to either a single direction path 522,as illustrated in FIG. 5G, or a two lane path 524, as illustrated inFIG. 5H, may apply simple local road rules employing give way rules. Forexample, an applied give way rule may be that a truck exiting the aislegives way to all traffic. In embodiments in which a single directionaisle is part of a serpentine arrangement, for example, no conflictexists between trucks entering and leaving the aisle.

Referring to FIG. 5I, a bi-directional traffic in aisle intersection 526is illustrated as a more complex intersection. In embodiments, smarttraffic lights may be employed but would need to be employed for eachaisle. Further, knowledge of a current materials handling vehicleoccupancy of each aisle and the intent of the materials handlingvehicles at the entry and exit points of each aisle would be needed tomanage traffic.

Referring to FIG. 6, a block diagram illustrates a system including acomputing device 700, through which embodiments of the disclosure can beimplemented. The computing device 700 described herein is but oneexample of a suitable computing device and does not suggest anylimitation on the scope of any embodiments presented. The computingdevice 700 may be communicatively coupled to one or more computingdevices through a warehouse management system. Nothing illustrated ordescribed with respect to the computing device 700 should be interpretedas being required or as creating any type of dependency with respect toany element or plurality of elements. In various embodiments, acomputing device 700 may include, but need not be limited to, a desktop,laptop, server, client, tablet, smartphone, or any other like device. Inembodiments, the computing device 700 may be part of the materialshandling vehicle system of an autonomous or semi-autonomous system asdescribed herein. In an embodiment, the computing device 700 includes atleast one processor 702 and memory (non-volatile memory 708 and/orvolatile memory 710). In embodiments, one or more unique identifiers 728for respective intersections as described herein and/or one or morewarehouse maps 730 may be stored in the memory. The computing device 700can include one or more displays and/or output devices 704 such asmonitors, speakers, headphones, projectors, wearable-displays,holographic displays, and/or printers, for example. Output devices 704may be configured to output audio, visual, and/or tactile signals andmay further include, for example, audio speakers, devices that emitenergy (radio, microwave, infrared, visible light, ultraviolet, x-rayand gamma ray), electronic output devices (Wi-Fi, radar, laser, etc.),audio (of any frequency), etc.

The computing device 700 may further include one or more input devices706 which can include, by way of example, any type of mouse, keyboard,disk/media drive, memory stick/thumb-drive, memory card, pen,touch-input device, biometric scanner, voice/auditory input device,motion-detector, camera, scale, and the like. Input devices 706 mayfurther include sensors, such as biometric (voice, facial-recognition,iris or other types of eye recognition, hand geometry, fingerprint, DNA,or any other suitable type of biometric data, etc.), video/still images,motion data (accelerometer, GPS, magnetometer, gyroscope, etc.) andaudio (including ultrasonic sound waves). Input devices 706 may furtherinclude cameras (with or without audio recording), such as digitaland/or analog cameras, still cameras, video cameras, thermal imagingcameras, infrared cameras, cameras with a charge-couple display,night-vision cameras, three-dimensional cameras, webcams, audiorecorders, and the like.

The computing device 700 typically includes non-volatile memory 708(ROM, flash memory, etc.), volatile memory 710 (RAM, etc.), or acombination thereof. A network interface hardware 712 can facilitatecommunications over a network 714 via wires, via a wide area network,via a local area network, via a personal area network, via a cellularnetwork, via a satellite network, etc. Suitable local area networks mayinclude wired Ethernet and/or wireless technologies such as, forexample, wireless fidelity (Wi-Fi). Suitable personal area networks(such as of a locally mediated embodiment of a traffic management systemas described herein) may include wireless technologies such as, forexample, IrDA, Bluetooth, Wireless USB, Z-Wave, ZigBee, and/or othernear field communication protocols. Suitable personal area networks maysimilarly include wired computer buses such as, for example, USB andFireWire. Suitable cellular networks include, but are not limited to,technologies such as LTE, WiMAX, UMTS, CDMA, and GSM. Network interfacehardware 712 can be communicatively coupled to any device capable oftransmitting and/or receiving data via the network 714. Accordingly, thenetwork interface hardware 712 can include a communication transceiverfor sending and/or receiving any wired or wireless communication. Forexample, the network interface hardware 712 may include an antenna, amodem, LAN port, Wi-Fi card, WiMax card, mobile communications hardware,near-field communication hardware, satellite communication hardwareand/or any wired or wireless hardware for communicating with othernetworks and/or devices.

A computer-readable storage medium 716 may comprise a plurality ofcomputer readable mediums, each of which may be either a computerreadable storage medium or a computer readable signal medium. A computerreadable storage medium 716 may be non-transitory in that it excludesany transitory, propagating signal as a storage medium and may reside,for example, within an input device 706, non-volatile memory 708,volatile memory 710, or any combination thereof. A computer readablestorage medium can include tangible media that is able to storeinstructions associated with, or used by, a device or system. A computerreadable storage medium includes, by way of example: RAM, ROM, cache,fiber optics, EPROM/Flash memory, CD/DVD/BD-ROM, hard disk drives,solid-state storage, optical or magnetic storage devices, diskettes,electrical connections having a wire, or any combination thereof. Acomputer readable storage medium may also include, for example, a systemor device that is of a magnetic, optical, semiconductor, or electronictype. Computer readable storage media and computer readable signal mediaare mutually exclusive.

A computer readable signal medium can include any type of computerreadable medium that is not a computer readable storage medium and mayinclude, for example, propagated signals taking any number of forms suchas optical, electromagnetic, or a combination thereof. A computerreadable signal medium may include propagated data signals containingcomputer readable code, for example, within a carrier wave. Computerreadable storage media and computer readable signal media are mutuallyexclusive.

The computing device 700 may include one or more network interfaces(i.e., network interface hardware 712) to facilitate communication withone or more remote devices, which may include, for example, clientand/or server devices. A network interface hardware 712 may also bedescribed as a communications module, as these terms may be usedinterchangeably. For clarity, it is noted that usage of the term“communication” herein, with respect to FIG. 6, or elsewhere, may referto one-way communication or two-way communication.

For the purposes of describing and defining the present invention, it isnoted that reference herein to a variable, result, action,determination, condition, or other object being “based on” a particularcondition is not intended to denote that the object is exclusively basedon the condition. Rather, reference herein to an object that is “based”on a particular condition is intended to be open ended such that theobject may be based on a single condition or a plurality of conditions.

It is also noted that recitations herein of “at least one” component,element, etc., should not be used to create an inference that thealternative use of the articles “a” or “an” should be limited to asingle component, element, etc.

It is noted that recitations herein of a component of the presentdisclosure being “configured” in a particular way, to embody aparticular property, or to function in a particular manner, arestructural recitations, as opposed to recitations of intended use. Morespecifically, the references herein to the manner in which a componentis “configured” denotes an existing physical condition of the componentand, as such, is to be taken as a definite recitation of the structuralcharacteristics of the component.

Having described the subject matter of the present disclosure in detailand by reference to specific embodiments thereof, it is noted that thevarious details disclosed herein should not be taken to imply that thesedetails relate to elements that are essential components of the variousembodiments described herein, even in cases where a particular elementis illustrated in each of the drawings that accompany the presentdescription. Further, it will be apparent that modifications andvariations are possible without departing from the scope of the presentdisclosure, including, but not limited to, embodiments defined in theappended claims. More specifically, although some aspects of the presentdisclosure are identified herein as preferred or particularlyadvantageous, it is contemplated that the present disclosure is notnecessarily limited to these aspects.

1. A traffic management system comprising a traffic management mediatorand a plurality of materials handling vehicles, each of the plurality ofmaterials handling vehicles comprising a vehicle body, a plurality ofvehicle wheels, a traction control unit, a braking system, a steeringassembly, and a navigation subsystem, wherein: the plurality ofmaterials handling vehicles are configured to navigate a vehicle transitsurface in a warehouse environment; the plurality of vehicle wheelssupport the vehicle body; the traction control unit, the braking system,and the steering assembly, are operatively coupled to one or more of theplurality of vehicle wheels; the navigation subsystem is configured tocooperate with the traction control unit, the braking system, and thesteering assembly to navigate a respective materials handling vehicle ofthe plurality of materials handling vehicles along the vehicle transitsurface in the warehouse environment; and the traffic managementmediator is configured to cooperate with the navigation subsystems ofthe plurality of materials handling vehicles to: receive a request fromthe navigation subsystem of a target materials handling vehicle toproceed through an intersection; determine whether a prior request toproceed through the intersection has been received from a differentmaterials handling vehicle; determine whether the prior requestcomprises a corresponding exit notification indicating that thedifferent materials handling vehicle has progressed through and exitedfrom the intersection; transmit permission for the target materialshandling vehicle to proceed through the intersection to the navigationsubsystem of the target materials handling vehicle in response to adetermination that (i) the traffic management mediator has not receivedthe prior request from the different materials handling vehicle or (ii)the prior request from the different materials handling vehiclecomprises the corresponding exit notification; and navigate the targetmaterials handling vehicle through the intersection based on thetransmission of the permission to proceed through the intersection. 2.The traffic management system of claim 1, wherein the traffic managementmediator is one or remote from or local with respect to and associatedwith the intersection.
 3. The traffic management system of claim 1,wherein the traffic management mediator is local with respect to andassociated with the intersection, and wherein the navigation subsystemis further configured to navigate the target materials handling vehiclethrough the intersection utilizing an associated set of road rules. 4.The traffic management system of claim 3, wherein the traffic managementmediator comprises one or more smart traffic lights configured tocommunicate electronically with the navigation subsystem of each of theplurality of materials handling vehicles.
 5. The traffic managementsystem of claim 1, wherein the navigation subsystem is furtherconfigured to: transmit a corresponding exit notification to the trafficmanagement mediator upon exit of the target materials handling vehiclefrom the intersection.
 6. The traffic management system of claim 1,wherein the navigation subsystem is configured to determine whether thetarget materials handling vehicle is approaching, or has arrived at, theintersection by: establishing or recognizing an entry zone associatedwith the intersection; and indicating a presence of the target materialshandling vehicle in the entry zone.
 7. The traffic management system ofclaim 6, wherein the navigation subsystem establishes the entry zone asa virtual boundary in the warehouse environment or recognizes a literalentry zone defined by boundary elements in the warehouse environment. 8.The traffic management system of claim 1, wherein the navigationsubsystem is further configured to: determine whether the targetmaterials handling vehicle is approaching, or has arrived at, theintersection; and transmit the request to proceed through theintersection in response to a determination that the target materialshandling vehicle is approaching, or has arrived at, the intersection. 9.The traffic management system of claim 8, wherein the navigationsubsystem is further configured to: receive a wait request from thetraffic management mediator in response to the transmitted request; andtransmit a re-request to proceed through the intersection in response tothe wait request after a period of time.
 10. The traffic managementsystem of claim 9, wherein the period of time is in a range of from 5seconds to 10 seconds.
 11. The traffic management system of claim 9,wherein the traffic management mediator is further configured to:generate an alert for an inspection of the intersection in response tothe wait request continuing for over one minute.
 12. The trafficmanagement system of claim 8, wherein the navigation subsystem isconfigured to determine whether the target materials handling vehicle isapproaching, or has arrived at, the intersection by interacting with alocalization subsystem to determine a position and heading of the targetmaterials handling vehicle relative to the intersection.
 13. The trafficmanagement system of claim 1, wherein the navigation subsystem isfurther configured to: navigate the target materials handling vehiclethrough the intersection utilizing an associated set of road rules. 14.The traffic management system of claim 10, wherein the associated set ofroad rules accounts for vehicle positioning relative to theintersection, intersection characteristics defining the intersection, orboth.
 15. The traffic management system of claim 1, wherein thenavigation subsystem is further configured to: determine whether thetarget materials handling vehicle is approaching, or has arrived at, theintersection by interacting with a localization subsystem to determine aposition and heading of the target materials handling vehicle relativeto the intersection; transmit the request to proceed through theintersection in response to a determination that the target materialshandling vehicle is approaching, or has arrived at, the intersection;receive a wait request from the traffic management mediator in responseto the transmitted request; and transmit a re-request to proceed throughthe intersection in response to the wait request after a period of time;generate an alert for an inspection of the intersection in response tothe wait request continuing for over one minute; receive a clearance ofthe alert for the inspection upon determination that the intersection isclear; navigate the target materials handling vehicle through theintersection utilizing an associated set of road rules based on thetransmission of the permission to proceed through the intersection andthe clearance, wherein the associated set of road rules accounts forvehicle positioning relative to the intersection, intersectioncharacteristics defining the intersection, or both.
 16. A method ofnavigating a plurality of materials handling vehicles with respect to avehicle transit surface in a warehouse environment, comprising:utilizing at least one the plurality of materials handling vehiclesdisposed on the vehicle transit surface, each of the plurality ofmaterials handling vehicles comprising a vehicle body, a plurality ofvehicle wheels supporting the vehicle body, a traction control unit, abraking system, and a steering assembly, the traction control unit, thebraking system, and the steering assembly operatively coupled to one ormore of the plurality of vehicle wheels, and a navigation subsystem,wherein the navigation subsystem is configured to cooperate with thetraction control unit, the braking system, and the steering assembly;utilizing a traffic management mediator configured to cooperate with thenavigation subsystems of the plurality of materials handling vehicles;receiving a request from the navigation subsystem of a target materialshandling vehicle to proceed through an intersection; determining whethera prior request to proceed through the intersection has been receivedfrom a different materials handling vehicle; determining whether theprior request comprises a corresponding exit notification indicatingthat the different materials handling vehicle has progressed through andexited from the intersection; transmitting permission for the targetmaterials handling vehicle to proceed through the intersection to thenavigation subsystem of the target materials handling vehicle inresponse to a determination that (i) the traffic management mediator hasnot received the prior request from the different materials handlingvehicle or (ii) the prior request from the different materials handlingvehicle comprises the corresponding exit notification; and navigatingthe target materials handling vehicle through the intersection based onthe transmission of the permission to proceed through the intersection.17. The method of claim 16, wherein the traffic management mediator isremote from the intersection, local with respect to and associated withthe intersection, or combinations thereof.
 18. The method of claim 17,wherein the traffic management mediator comprises one or more smarttraffic lights configured to communicate electronically with thenavigation subsystem of each of the plurality of materials handlingvehicles when the traffic management mediator is local with respect toand associated with the intersection.
 19. The method of claim 16,further comprising: transmitting from the navigation subsystem acorresponding exit notification to the traffic management mediator uponexit of the target materials handling vehicle from the intersection. 20.The method of claim 16, further comprising: determining by thenavigation subsystem whether the target materials handling vehicle isapproaching, or has arrived at, the intersection; and transmitting fromthe navigation subsystem to the traffic management mediator the requestto proceed through the intersection in response to a determination thatthe target materials handling vehicle is approaching, or has arrived at,the intersection.